So I have had 2 40Ds so far and use them professionally for a newspaper.
Anyone giving advice on the 50D, forget it. By far the worst performer out of the 3. As they just crammed 33% more pixels onto the same sensor without any change in tech. Apart from the screen the 40D is better option and cheaper.
I have been waiting for the 5D MKIII and will pull the trigger but like to leave it a while and let the price simmer, make sure there arent any more problems, I like to get as much profit out of all my gear. Anyway the resolution is fine for newspaper work as you basically print on toilet paper. So my 40D became very temperamental last week and has hit 139,000 actuations and didnt want to spend any money on it. So on Saturday became the owner of a 7D.
So I was never that keen on buying any of the 18mp variations of this generation as all the reviews and opinions on here have pointed out how the noise isnt that great and slightly worse than the older generation low down in the ISO. So was waiting for the new gen to see what they offer, but I needed something to fill in for the next couple of months. I found a local guy selling his 7D, year old, less than 10k clicks used completely for amateur stuff. Had a couple of scratches but as my cameras are work horses not museum pieces that didnt bother me. Anyway was on ebay offered him £750 cash so he saves the fees. Camera bought.
First impressions... the build quality seems slightly worce than the 40D on the plastic areas. Card door creaks and the plastic has more give in that area where you grip. But the problem seems fairly common on the 5D MKII and 7D after a quick google, a bit of insulation tape solved that.
Feels lighter although its not. The speed is fantastic although only 1.5 frames more it is really noticeable. The screen is incredible! Really great, one of the worst parts of the 40D. The AF is out of this world in comparison to the old 9 point, although you can overcome the downfalls of the 40Ds 9 point the 7Ds helps for every situation you are thrown into with the different modes, especially when using F2.8 lenses. I can see much more keepers. Also has the movie mode which isnt a deal breaker for me but useful. Micro adjust a must have feature! Get the most from those lenses. Half a stop more of dynamic range, 80% more resolution. Slightly better at high ISO probably 1/2 a stop, 100% viewfinder coverage and larger maximum ISO from 3200 to 12800 so 2 stops and useful.
If you are after a dramatic increase in IQ your heading in the wrong direction. It is better but bread and butter it aint, the pro you can take from this is that you can print much larger at about the same quality. Also ISO 100-400 it seems it is very slightly noisy but negligible! Seriously negligible! Over 1600 it is good but not night and day but useable. Banding is better than the 40D.
Just this eve had a quick test against the 40D. The 7D isnt bad.. 80% more resolution and about the same noise level up to 1250 past 1600 its a tad better maybe one stop and goes to 12800, add that awesome AF, and screen res its not bad. But if the 40D wasnt on its last legs.. worthwhile upgrade.. debatable. But that AF is worth having it for, on its own and the screen. But I already have the glass so its just the body I have to worry about.
Think you can read too much, the noise issue really is negligible in real life, I have no issue using it professionally. DR could be better but acceptable. Compared to full frame alternatives it has its draw backs with IQ and DR but what it lacks there it makes up in other areas. Full frame is slightly overkill for me anyway but will get one to go with the 7D. I like the extra length you get from the longer lenses with crop APC.
Like others have said get some glass. A 17-55mm F2.8 would be great also a 10-22mm and a 70-200mm F2.8 makes the 40D awesome. The 24-105mm I cant recommend for APC simply because the widest you get is 38.4mm and as an everyday lens its not wide enough, great lens but not suitable. Need two lenses to cover a normal focal length, but obv a pain if going FF in the future. But from the current lenses I would suggest staying APC.
If you want a 7D go get one! Its a good camera, but again with 80% more resolution you need the glass to resolve it so it would be an expensive upgrade for glass and the camera. So I suggest getting some nice glass as its a good camera and still keeps up with todays offerings. The 40D was one of those cameras that was unique and a great camera, still holds its own now.
Hope this helps.